Dear all,

starting with Fortran 2018, DATE_AND_TIME allowed a non-default
integer VALUES argument.

While gfortran accepts this silently, this failed at runtime
because the library implementation beyond kind=4 and kind=8
was missing.

Futhermore, the standard effectively requires that the integer
kind is at least 2.  The attached patch adds several checks,
plus adds checking for the array size to be sufficient, extends
the implementation to the remaining kinds, and corrects several
issues in the related documentation.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

Thanks,
Harald